Methods to form self-aligned permanent on-chip interconnect structures

ABSTRACT

Methods of fabricating a self-aligned permanent on-chip interconnect structure are provided. In one embodiment, the method includes forming a patterned photoresist having at least one opening on a surface of a substrate. A dielectric sidewall structure is then formed on each sidewall of the patterned photoresist and within the at least one opening. A narrowed width opening is present between neighboring dielectric sidewall structures. The patterned photoresist is then removed and thereafter each dielectric sidewall structure is converted into a permanent patterned dielectric structure which is self-aligned and double patterned. At least an electrically conductive material is formed within the narrowed width openings.

FIELD OF THE INVENTION

The present disclosure relates to semiconductor interconnect structuresand methods of fabricating the same. More particularly, the presentdisclosure relates to methods of forming self-aligned permanent on-chipinterconnect structures that include cured dielectric sidewallstructures as permanent on-chip insulators using a self-aligned singleexposure, double patterning technique.

BACKGROUND

It is widely known that the speed of propagation of interconnect signalsis one of the most important factors controlling overall circuit speedas feature sizes are reduced and the number of devices per unit area aswell as the number of interconnect levels are increased. Throughout thesemiconductor industry, there has been a strong drive to reduce thedielectric constant, k, of the interlayer dielectric (ILD) materialsused to electrically insulate metal lines. As a result, interconnectsignals travel faster through conductors due to a reduction inresistance-capacitance (RC) delays.

State-of-the-art semiconductor chips employ copper (Cu) as theelectrical conductor and inorganic organosilicates as the low dielectricconstant (low k) dielectric, and have up to twelve levels of Cu/low kinterconnect layers. These Cu/low k interconnect layers are fabricatedwith an iterative additive process, called dual damascene, whichincludes several processing steps including, for example, filmdeposition, patterning by lithography and reactive ion etching, liner(Cu barrier) deposition, Cu metal fill by electrochemical plating, andchemical-mechanical polishing of excessive Cu metal; these steps aredescribed in greater detail in the following paragraphs.

When fabricating integrated circuit wiring within a multi-layerinterconnect scheme, an insulating or dielectric material, e.g., siliconoxide or a low k insulator will normally be patterned with at leastseveral thousand openings to create conductive line openings and/or viaopenings using photo patterning and plasma etching techniques, e.g.,photolithography with a photoresist subsequently followed by etching byplasma processes. These via and line openings are typically filled witha conductive metal material, e.g., aluminum, copper, or their alloysetc., to interconnect the active and/or passive elements of theintegrated circuits. The semiconductor device is then polished to levelits surface.

A continuous cap layer is then normally deposited over the planarizedsurface featuring the dielectric material and conductive metal material.Next, a dielectric material is deposited over the continuous cap layer,via and conductive line openings are created again within the dielectriclayer as before, another conductive metal material is deposited withinthe openings and another continuous cap layer is deposited thereon. Theprocess is repeated to fabricate a multi-layer interconnect wiringsystem. The multi-layer interconnect system built thereby is referred toin the art as a dual damascene integration scheme.

Unfortunately, the strategy to introduce low k materials (typicallydielectrics whose dielectric constant is below that of silicon oxide)into advanced interconnects is difficult to implement due to the newmaterials chemistry of the low k materials that are being introduced.Moreover, low k materials exhibit fundamentally weaker electrical andmechanical properties as compared to silicon oxide. Further, thepatterned dielectric alternatives are typically susceptible to damageduring the various interconnect processing steps. The damage observed inthe low k materials is manifested by an increase in the dielectricconstant and increased moisture uptake, which may result in reducedperformance and device reliability.

Optical lithography has been the workhorse to continuously shrink (orscale) semiconductor devices and their related interconnect structures.Traditional scaling by optical lithography has been achieved with onesingle exposure mostly by reduction in the wavelength of the lightsources, new tool design (higher numerical aperture or NA), improvedlithographic materials or a combination thereof. Recently, multiplepatterning, particularly double patterning techniques, where oneparticular level of circuitry is patterned by exposing the wafer to thelight sources using two mask sets, has become increasingly necessary tomaintain the pace of scaling at 193 nm optical wavelength. This type ofdouble patterning necessitates significantly increase in complexity andthe attendant increased manufacturing costs. Furthermore, this type ofdouble patterning requires precise placement of the second exposure overthe patterns formed by the first exposure. Any imperfect placement, ormis-alignment or overlay error, can cause degradation in performance orreliability or both. Such mis-alignment is due to the limitation of thelithographic tool employed or processing errors.

One way to overcome the integration challenges of low k materialsmentioned above is to protect low k materials by adding at least onesacrificial hardmask layer onto a surface of the low k material. Whilethe hardmask layer serves to protect the low k material, the presence ofthe sacrificial hardmask layer adds enormous process complexity andmanufacturing as additional film deposition, pattern transfer etch, andremoval of the hardmask layers are needed.

A state-of-the-art back-end-of-the-line (BEOL) integration process,called a low temperature oxide (LTO) process, employs up to eight layersof sacrificial hardmask materials to fabricate a two-layer dualdamascene interconnect structure.

For example, a via-first LTO integration for forming a dual damasceneinterconnect includes the steps of: depositing a dielectric material ona substrate including a patterned conductor; forming at least one via inthe dielectric material, such that at least one of the vias ispositioned over the patterned conductor; depositing a layer ofplanarizing material on the dielectric material and in the via;depositing a layer of barrier material on the layer of planarizingmaterial; depositing at least one layer of imaging material on the layerof barrier material; forming at least one trench in the imagingmaterial, barrier material and planarizing material, such that the atleast one trench is positioned over the via; removing the imagingmaterial, either after or concurrently with forming the trench in theplanarizing material; transferring the at least one trench to thedielectric material, such that at least one of the trenches ispositioned over the via; removing the barrier material, either after orconcurrently with transferring the at least one trench to the dielectricmaterial; and removing the planarizing material.

A line-first LTO integration for forming a dual damascene interconnectstructure includes the steps of: depositing a dielectric material on asubstrate including a patterned conductor; forming at least one trenchin the dielectric material, such that the at least one trench ispositioned over the patterned conductor; depositing a layer ofplanarizing material on the dielectric material and in the trench;depositing a layer of barrier material on the layer of planarizingmaterial; depositing at least one layer of imaging material on the layerof barrier material; forming at least one via in the imaging material,barrier material and planarizing material, such that at least one of thevias is positioned over the trench and the patterned conductor; removingthe imaging material, either after or concurrently with forming the viain the planarizing material; transferring the at least one via to thedielectric material, such that at least one of the vias is positionedover the trench and the patterned conductor; removing the barriermaterial, either after or concurrently with transferring the at leastone via to the dielectric material; and removing the planarizingmaterial.

The prior art dual damascene integration schemes, such as the LTO onementioned above, are very complex, inefficient, and costly. For example,the via-first LTO integration scheme requires ten layers of films andtwenty-one process steps to form a two-layer dual damascene dielectricstructure. In other words, 80% of the films are not needed in the finalinterconnect structure.

Although immensely popular in semiconductor manufacturing, the prior artdual damascene integration scheme described above suffers from severaldrawbacks including, for example, First, it constitutes a significantportion of manufacturing cost of advanced semiconductor chips as manylayers, up to twelve layers for the state-of-the-art chips, are requiredto connect the minuscule transistors within a chip and to the printedcircuit board. Second, it is a main yield detractor as the many layersof films required to form the interconnects generate chances for defectintroduction and, thus, degrade manufacturing yields. Third, it is veryinefficient and embodies enormous complexity. The current dual damasceneintegration scheme requires many sacrificial films (80% of the filmstack) to pattern and protect the fragile interlayer dielectric filmsfrom damage during processing. These sacrificial patterning andprotective films have to be removed after patterning and copper plating.Fourth, the performance gain by introduction of new lower-k materials isoften offset by the need for higher-k non-sacrificial protectivematerials, such as a cap layer, a hardmask layer, or a thicker copperbarrier layer. Fifth, the prior art complex dual damascene processlengthens manufacturing turn-around time and R&D development cycle.Sixth, the plasma etching process is an expensive and often unreliableprocess and requires significant up-front capital investment. Seventh,the aforementioned mis-alignment during double exposure, doublepatterning can cause degradation in performance and reliability of theresultant chips.

In view of the above, there is a need to simplify the formation ofdouble patterned interconnects, including dielectrics for improvedperformance, reliability, cost-saving and manufacturing efficiencywithout mis-alignment as in the case with a traditional double exposurepatterning scheme.

SUMMARY

Simplified methods of fabricating a self-aligned permanent on-chipinterconnect structure are provided. In some embodiments, the presentdisclosure provides an interconnect structure with differently sizedconductive features on the same interconnect level. By “differentlysized” it is meant that some of the conductive features within the sameinterconnect level have different widths.

The methods of this disclosure utilize a single exposure, doublepatterning technique. In particular, the methods of the presentdisclosure include providing a patterned photoresist and then formingdielectric sidewall structures on the sidewalls of the patternedphotoresist. The dielectric sidewall structures are comprised of adielectric coating material that can be crosslinked with residual acidpresent in the sidewalls of the patterned photoresist and can form apermanent patterned dielectric material upon subsequent curing. Moreparticularly, the dielectric coating material includes a polymer,copolymer or blend of polymers and/or copolymers having at least onereactive group. The term “at least one reactive group” when referring tothe dielectric coating material denotes one or more acid-sensitivereactive groups. The methods of the present disclosure improveresolution and the placement of the structure since a self-alignedsidewall double patterning technique is employed.

In one embodiment, the method includes forming a patterned photoresisthaving at least one opening on a surface of a substrate. Dielectricsidewall structures are then formed on each sidewall of the patternedphotoresist and within the at least one opening. An opening is locatedbetween neighboring dielectric sidewall structures that has a narrowerwidth than that of the at least one opening in the patternedphotoresist. The opening between neighboring dielectric structures isreferred to herein as a “narrowed width opening”. The patternedphotoresist is then removed to provide additional second openingsbetween neighboring dielectric sidewall structures and thereafter eachdielectric sidewall structure is converted into a permanent patterneddielectric structure. The converting of each dielectric sidewallstructure into a permanent patterned dielectric structure can beachieved by curing. At least an electrically conductive material isformed within at least each narrowed width opening and the additionalopenings that are located between neighboring permanent patterneddielectric structures. The size of the narrowed width openings can bethe same as, or different from, that of the additional openings formedby removal of the patterned photoresist.

In some embodiments, the method further includes etching portions of thesubstrate that are exposed by the narrowed width openings and additionalopenings prior to forming the electrically conductive material. Theetching of portions of the substrate can occur prior to, or after,converting the dielectric sidewall structures into permanent patterneddielectric structures.

The dielectric sidewall structures are formed by overfilling the atleast one opening with a dielectric coating material. After theoverfilling step, a baking step is performed to cause diffusion ofresidual acid from sidewalls of the patterned photoresist intoneighboring sidewall portions of the dielectric coating material andcros slinking of the neighboring sidewall portions of the dielectriccoating material. The non-crosslinked portions of the dielectric coatingmaterial are then removed relative to the crosslinked neighboringsidewall portions of the dielectric coating material by rising with anappropriate solvent or solution.

In another embodiment of the present disclosure, a dual damascene methodis provided that includes providing a patterned dielectric materialhaving a plurality of first openings on an upper surface of a substrate;forming a patterned photoresist having second openings atop thepatterned dielectric material, wherein a portion of the patternedphotoresist remains in at least one of the plurality of first openings;forming a dielectric sidewall structure on each sidewall of thepatterned photoresist within said second openings and atop an uppersurface of the patterned dielectric material, wherein said dielectricsidewall structure narrows the second openings providing narrowed widthsecond openings; removing the patterned photoresist to provide a thirdopening between neighboring dielectric sidewall structures, wherein saidnarrowed width second openings and said third opening are located atopand are connected with one of said plurality of first openings;converting each dielectric sidewall structure into a self-alignedpermanent patterned dielectric structure; and filling each opening withat least an electrically conductive material. The sizes of the first,the narrowed width second and the third openings can be the same ordifferent.

In another aspect of the present disclosure, an interconnect structure(single damascene and dual damascene) is provided in which differentlysized conductive features are present at a same interconnect level. Thedifferently sized conductive features are laterally adjacent each other.That is, differently sized conductive features all have bottom surfaceslocated at a same horizontal level (e.g., plane) within the interconnectstructure and top surfaces that are located on a same horizontal level(e.g., plane) within the interconnect structure. The differently sizedconductive features are formed in some embodiments depending on thewidth of each dielectric sidewall structure formed. In general terms, aninterconnect structure is provided that includes at least one permanentpatterned dielectric layer located on a substrate, wherein said at leastone permanent patterned dielectric layer includes differently sizedconductive features embedded therein, said different sized conductivefeatures are laterally adjacent to each other and are located at a sameinterconnect level.

The at least one patterned dielectric layer mentioned above is comprisedof a cured reaction product of an acid catalyzed crosslinkedfunctionalized polymer, copolymer, or a blend including at least two ofany combination of polymers and/or copolymers having one or moreacid-sensitive reactive groups.

A dielectric composition is also provided herein that includes afunctionalized polymer, copolymer, or a blend including at least two ofany combination of polymers and/or copolymers having one or moreacid-sensitive reactive groups; and at least one solvent that iscompatible with photoresist patterns. By “compatible with”, it is meantthat the application of the dielectric composition directly over thephotoresist patterns does not substantially alter the size, the shape,and other features of the photoresist patterns.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial representation (through a cross sectional view)illustrating an initial structure that can be employed in one embodimentof the present disclosure.

FIG. 2 is a pictorial representation (through a cross sectional view)illustrating the initial structure of FIG. 1 after forming a photoresiston an upper surface of the initial structure.

FIG. 3 is a pictorial representation (through a cross sectional view)illustrating the structure of FIG. 2 after forming at least one openingwithin the photoresist.

FIG. 4 is a pictorial representation (through a cross sectional view)illustrating the structure of FIG. 3 after forming dielectric sidewallstructures within the at least one opening and on sidewalls of thepatterned photoresist, wherein a narrowed width opening is presentbetween neighboring dielectric sidewall structures.

FIG. 5 is a pictorial representation (through a cross sectional view)illustrating the structure of FIG. 4 after removing the patternedphotoresist and converting the dielectric sidewall structures intopermanent low k structures.

FIG. 6 is a pictorial representation (through a cross sectional view)illustrating the structure of FIG. 5 after extending the at least onenarrowed width opening into at least a portion of the initial structure.

FIG. 7 is a pictorial representation (through a cross sectional view)depicting the structure of FIG. 6 after forming an electricallyconductive material within the extended at least one narrowed widthopening.

FIG. 8 is a pictorial representation (through a cross sectional view)illustrating the initial structure of FIG. 1 after forming a dielectricmaterial on the upper most surface of the initial structure inaccordance with another embodiment of the present disclosure.

FIG. 9 is a pictorial representation (through a cross sectional view)illustrating the structure of FIG. 8 after patterning the dielectricmaterial into a patterned dielectric material having a plurality offirst openings therein.

FIG. 10 is a pictorial representation (through a cross sectional view)illustrating the structure of FIG. 9 after forming a photoresist on thepatterned dielectric material and within at least one of said pluralityof first openings in said patterned dielectric material.

FIG. 11 is a pictorial representation (through a cross sectional view)illustrating the structure of FIG. 10 after patterning the photoresist,wherein second openings are present in the patterned resist.

FIG. 12 is a pictorial representation (through a cross sectional view)illustrating the structure of FIG. 10 after forming dielectric sidewallstructures on sidewalls of the patterned photoresist, wherein thedielectric sidewall structures narrow the width of the second openingsproviding narrowed width second openings.

FIG. 13 is a pictorial representation (through a cross sectional view)illustrating the structure of FIG. 12 after removing the patternedphotoresist and converting the dielectric sidewall structures intopermanent patterned dielectric structures.

FIG. 14 is a pictorial representation (through a cross sectional view)illustrating the structure of FIG. 13 after etching exposed portions ofthe initial structure.

FIG. 15 is a pictorial representation (through a cross sectional view)illustrating the structure of FIG. 14 after filling the various openingswith at least an electrically conductive material.

DETAILED DESCRIPTION

The present disclosure, which provides self-aligned sidewall doublepatterning techniques and interconnect structures that are formed by thesame, will now be described in greater detail by referring to thefollowing discussion and drawings that accompany the presentapplication. It is observed that the drawings of the present applicationare provided for illustrative proposes and, as such, the drawings arenot drawn to scale.

In the following description, numerous specific details are set forth,such as particular structures, components, materials, dimensions,processing steps and techniques, in order to provide an understanding ofsome aspects of the present invention. However, it will be appreciatedby one of ordinary skill in the art that the invention may be practicedwithout these specific details. In other instances, well-knownstructures or processing steps have not been described in detail inorder to avoid obscuring the invention.

It will be understood that when an element as a layer, region orsubstrate is referred to as being “on” or “over” another element, it canbe directly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “beneath” or “under” another element, it can bedirectly beneath or under the other element, or intervening elements maybe present. In contrast, when an element is referred to as being“directly beneath” or “directly under” another element, there are nointervening elements present.

Reference is first made to FIGS. 1-7 which illustrate one embodiment ofthe present disclosure. Specifically, FIGS. 1-7 illustrate an embodimentin which a single damascene interconnect structure is formed using aself-aligned sidewall double patterning technique in accordance with thepresent disclosure.

Referring first to FIG. 1, there is illustrated an initial structure 10that can be employed in one embodiment of the present disclosure. Theinitial structure 10 of FIG. 1 includes a substrate 12, an optionaldielectric cap 14 and an antireflective coating (ARC) 16. The ARC 16 maybe located on an upper surface of the optional dielectric cap 14, ifpresent. Alternatively, and when the optional dielectric cap 14 is notpresent, the ARC 16 is located on an upper surface of substrate 12.

Substrate 12 may comprise a semiconducting material, an electricallyinsulating material, an electrically conductive material, devices orstructures made of these materials or any combination thereof (e.g., alower level of an interconnect structure). When the substrate 12 iscomprised of a semiconducting material, any semiconductor such as Si,SiGe, SiGeC, SiC, Ge alloys, GaAs, InAs, InP and other III/V or II/VIcompound semiconductors, or organic semiconductors may be used.Substrate 12 may also be a flexible substrate containing devices thatare suitable for high-speed roll-to-roll processing. In addition tothese listed types of semiconducting materials, substrate 12 may also bea layered semiconductor such as, for example, Si/SiGe, Si/SiC,silicon-on-insulators (SOIs) or silicon germanium-on-insulators (SGOIs).These semiconductor materials may form a device, or devices orstructures, which may be discrete or interconnected. These devices anddevice structures may be for computation, transmission, storage ordisplay of information, such as logic devices, memory devices, switchesor display devices. In some embodiments, one or more semiconductordevices such as, for example, complementary metal oxide semiconductor(CMOS) devices, strained silicon devices, carbon-based (e.g., carbonnanotubes and/or graphene) devices, phase-change memory devices,magnetic memory devices, magnetic spin switching devices, singleelectron transistors, quantum devices, molecule-based switches and otherswitching or memory devices that can be part of an integrated circuit,can be fabricated on the semiconducting material.

When the substrate 12 is an electrically insulating material, theinsulating material can be an organic insulator, an inorganic insulatoror a combination thereof including multilayers. The electricallyinsulating materials may be part of a device, or devices or structures,which may be discrete or interconnected. These devices and structuresmay be for logic applications or memory applications.

When the substrate 12 is an electrically conducting material, thesubstrate may include, for example, polySi, an elemental metal, an alloyincluding at least one elemental metal, a metal silicide, a metalnitride, carbon nanotubes, graphene or combinations thereof includingmultilayers.

When present, the optional dielectric cap 14 can be formed directly onan upper surface of substrate 12 utilizing a standard deposition processsuch as, for example, chemical vapor deposition (CVD), plasma enhancedchemical vapor deposition (PECVD), atomic layer deposition (ALD),chemical solution deposition, or evaporation. The optional dielectriccap 14 can include any suitable dielectric capping material such as, forexample, SiC, SiN, SiO₂, a carbon doped oxide, a nitrogen and hydrogendoped silicon carbide SiC(N,H) or multilayers thereof. The optionaldielectric cap 14 can be a continuous layer or a discontinuous layer.The optional dielectric cap 14 can be a layer with graded composition inthe vertical direction. The optional dielectric cap 14 can also be aselect cap, such as CoWP.

After deposition of the optional dielectric cap 14, a post depositiontreatment may be applied to the optional dielectric cap 14 to modify theproperties of either the entire layer or the surface of the optionaldielectric cap 14. This post deposition treatment can be selected fromheat treatment, irradiation of electromagnetic wave (such ofultra-violet light), particle beam (such as an electron beam, or an ionbeam), plasma treatment, chemical treatment through a gas phase or aliquid phase (such as application of a monolayer of surface modifier) orany combination thereof. This post-deposition treatment can be blanketor pattern-wise. The purpose of the post deposition treatment is toenhance the chemical, physical, electrical, and/or mechanical propertiesof the optional dielectric cap 14, such as adhesion strength. Thechemical properties include the nature and/or location of surfacefunctional groups, and hydrophilicity. The physical properties includedensity, moisture absorption, and heat conductivity. The mechanicalproperties include modulus, hardness, cohesive strength, toughness,resistance to crack and adhesion strength to its neighboring layers. Theelectrical properties include dielectric constant, electrical breakdownfield, and leakage current.

The heat treatment should be no higher than the temperature that theunderlying substrate 12 can withstand, usually 500° C. This heattreatment can be conducted in an inert environment or within a chemicalenvironment in a gas phase or a liquid phase. This treatment step may ormay not be performed in the same tool as that used in forming theoptional dielectric cap 14.

The post deposition treatment by irradiation of electromagnetic wave canbe by ultra-violet (UV) light, microwave and the like. The UV light canbe broadband with a wavelength range from 100 nm to 1000 nm. The postdeposition treatment can also be UV light generated by an excimer laseror other UV light source. The UV treatment dose can be a few mJ/cm² tothousands of J/cm². This irradiation treatment can be conducted atambient temperature or at an elevated temperature no higher than 500° C.This irradiation treatment can be conducted in an inert environment orwithin a chemical environment in a gas phase or a liquid phase. Thefollowing conditions can be employed for this aspect of the presentdisclosure: a radiation time from 10 sec to 30 min, a temperature fromroom temperature to 500° C., and an environment including vacuum, orgases such as, for example, inert gas, N₂, H₂, O₂, NH₃, hydrocarbon, andSiH₄. This treatment step may or may not be performed in the same toolas that used in forming the optional dielectric cap 14.

The post deposition treatment by plasma treatment can be selected froman oxidizing plasma, a reducing plasma or a neutral plasma. Oxidizingplasmas include, for example, O₂, CO, and CO₂. Reducing plasmas include,for example, H₂, N₂, NH₃, and SiH₄. The neutral plasmas include, forexample, Ar and He. A plasma treatment time from 1 sec to 10 min and aplasma treatment temperature from room temperature to 400° C. can beemployed. This treatment step may or may not be performed in the sametool as that used in forming the optional dielectric cap 14.

The post deposition chemical treatment may be conducted in a gas phaseor a liquid phase. The following conditions may be employed: a treatmenttime from 1 sec to 30 min, a temperature from room temperature (i.e.,from 20° C. to 30° C.) to 500° C. Chemicals suitable for this chemicaltreatment may be selected from any chemicals that improve chemical,physical, electrical, and/or mechanical properties of the dielectric caplayer, such as adhesion strength. This chemical treatment may penetratethe entire optional dielectric cap 14 or is limited only to the surfaceof the optional dielectric cap 14. Example chemicals include adhesionpromoters such as silanes, siloxanes and silylation agents. Thistreatment step may or may not be performed in the same tool as that usedin forming the optional dielectric cap 14.

The thickness of the optional dielectric cap 14 may vary depending onthe technique used to form the same as well as the material make-up ofthe layer. Typically, the optional dielectric cap 14 has a thicknessfrom 1 nm to 100 nm, with a thickness from 20 nm to 45 nm being moretypical.

As stated above, antireflective coating (ARC) 16 can be formed on asurface of the optional dielectric cap 14 if present, or directly on asurface of the substrate 12 when the optional dielectric cap 14 is notpresent. In some embodiments of the present disclosure, the ARC 16 canbe omitted from the initial structure 10.

The ARC 16 employed has all of the following general characteristics:(i) It acts as an ARC during a lithographic patterning process; (ii) Itwithstands high-temperature BEOL integration processing (up to 500° C.);(iii) It prevents poisoning of at least one of the overlying layers thatserve as a photoresist by the substrate; (iv) It provides vertical wallprofile and sufficient etch selectivity between one of the overlyinglayers and the ARC layer; (v) It serves as a permanent dielectric layerin a chip (low dielectric constant, preferably k<5, more preferablyk<3.6); and (vi) It is compatible with conventional BEOL integration andproduces reliable hardware. Further discussion is now provided forcharacteristics (i)-(v).

Characteristic (i) the ARC 16 acts as an antireflective coating (ARC)during a lithographic patterning process: ARC 16 may be designed tocontrol reflection of light that is transmitted through an overlyingphotoresist material, reflected off the substrate 12 and back into thephotoresist material, where it can interfere with incoming light andcause the photoresist material to be unevenly exposed. The ARC's opticalconstants are defined here as the index of refraction n and theextinction coefficient k. In general, ARC 16 can be modeled so as tofind optimum optical parameters (n and k values) of the ARC as well asoptimum thickness. The preferred optical constants of ARC 16 are in therange from n=1.2 to n=3.0 and k=0.01 to k=0.9, preferably n=1.4 to n=2.6and k=0.02 to k=0.78 at a wavelength of 365, 248, 193 and 157, 126 nmand extreme ultraviolet (13.4 nm, 6.7 nm) radiation. The opticalproperties and thickness of the ARC 16 are optimized to obtain optimalresolution, profile control and to maximize the process window of thephotoresist material during the subsequent patterning steps, which iswell known to those ordinarily skilled in the art.

Characteristic (ii) ARC 16 can withstand high-temperature BEOLintegration processing (up to 500° C.): ARC 16 must withstand the harshprocessing conditions during BEOL integration. These include hightemperature and intense UV cure. The process temperature can be as highas 450° C. The intensity of the light used in the UV cure process can beas high as tens of J/cm².

Characteristic (iii) ARC 16 prevents photoresist material poisoning bythe substrate: At least the photoresist material employed hereinincludes a chemically amplified resist. The photoresist material can bepoisoned by any basic containment from the underlying substrate, such asa SiCN cap layer. The ARC 16 must serve as a barrier layer to preventbasic contaminant from the underlying substrate from diffusing into thephotoresist material to poison the same.

Characteristic (iv) ARC 16 provides vertical wall profile and sufficientetch selectivity between the photoresist material and the ARC layer: ARC16 should provide sufficient reflectivity control with reflectivity fromthe underlying substrate under a particular lithographic wavelength ofless than 8%, preferably less than 5%, more preferably less than 2% andgenerate vertical side wafer profile. ARC 16 should also generateresidue-free patterns with no footing. Moreover, the adhesion of thephotoresist material should be sufficient to prevent pattern collapse.ARC 16 should also be designed such that the etch selectivity during asubsequent ARC/cap open process is sufficiently high so that the openingof the ARC/cap stack does not erode a significant portion of thephotoresist material and degrade significantly its pattern profile. Anetch selectivity (etch rate ratio of ARC/cap versus photoresistmaterial) is greater than 1, preferably greater than 3, more preferablegreater than 5.

Characteristic (v) ARC 16 serves as a permanent dielectric layer in achip: ARC 16 remains in the final interconnect structure as a permanentdielectric layer in a chip. Therefore, ARC 16 must meet the requirementsof an on-chip dielectric insulator, including electrical properties (lowdielectric constant: preferably k less than 5, and more preferably kless than 3.6; dielectric breakdown field: greater than 2 MV/cm,preferably greater than 4 MV/cm, and more preferably greater than 6MV/cm, leakage: less than 10⁻⁵ A/cm², preferably less than 10⁻⁷ A/cm²,and more preferably less than 10⁻⁹ A/cm²); mechanical properties(adhesion energy is equal to or greater than the cohesive energy of theweakest layer of the integrated film stack); and the ARC employed mustpass electrical and mechanical reliability tests.

The thickness of the ARC 16 may vary depending on the technique used toform the same as well as the material make-up of the layer. Typically,the ARC 16 has a thickness from 1 nm to 200 nm, with a thickness from 10nm to 140 nm being more typical. The ARC 16 may be inorganic or a hybridof inorganic and organic. The ARC 16 may be a single layer ormultilayer. ARC 16 may also be a graded ARC with graded composition inthe vertical direction.

Inorganic antireflective coatings, such as silicon oxynitride (SiON),silicon carbide (SiC), silicon oxycarbide (SiOC), SiCOH, siloxane,silane, carbosilane, oxycarbosilane, and silsesquioxane, either as apolymer or a copolymer may be employed as ARC 16 and may be deposited,for example, by plasma-enhanced chemical vapor deposition, spin-ontechniques, spray coating, dip coating, etc. ARC 16 may be a singlelayer or multilayer. When ARC 16 is a multilayer ARC, the deposition ofeach layer may be the same or a combination of deposition methods can beused. The chemical composition of ARC 16 may be uniform or graded alongthe vertical direction. After applying ARC 16 particularly those from aliquid phase, a post deposition baking step is usually required toremove unwanted components, such as solvent, and to effect crosslinking.The post deposition baking step of the ARC 16 is typically, but notnecessarily always, performed at a temperature from 80° C. to 300° C.,with a baking temperature from 120° C. to 200° C. being more typical.

In some embodiments, the as-deposited ARC may be subjected to a postdeposition treatment to improve the properties of the entire layer orthe surface of ARC 16. This post deposition treatment can be selectedfrom heat treatment, irradiation of electromagnetic wave (such asultra-violet light), particle beam (such as an electron beam, or an ionbeam), plasma treatment, chemical treatment through a gas phase or aliquid phase (such as application of a monolayer of surface modifier) orany combination thereof. This post-deposition treatment can be blanketor pattern-wise. The purpose of this post deposition treatment is toenhance the chemical, physical, electrical, and/or mechanical propertiesof ARC 16 and/or a film stack including ARC 16 and optional dielectriccap 14, such as adhesion strength. The chemical properties includenature and/or location of surface functional groups, and hydrophilicity.The physical properties include density, moisture absorption, and heatconductivity. The mechanical properties include modulus, hardness,cohesive strength, toughness, resistance to crack and adhesion strengthto its neighboring layers. The electrical properties include dielectricconstant, electrical breakdown field, and leakage current. Theconditions described above for the post treatment of the optionaldielectric cap 14 may be used for the post treatment for the ARC.

In one embodiment, the ARC 16 that is employed is an inorganiccomposition that includes elements of M, C (carbon) and H (hydrogen),wherein M is selected from at least one of the elements of Si, Ge, B,Sn, Fe, Ta, Ti, Ni, Hf and La. Such an ARC is described, for example, inU.S. Patent Publication No. 2009/0079076 the entire content of which isincorporated herein by reference. This inorganic ARC may optionallyinclude elements of O, N, S, F or mixtures thereof. In some embodiments,M is preferably Si. In some embodiments, the ARC composition may also bereferred to as a vapor deposited M:C:H: optionally X material, wherein Mis as defined above, C and H are carbon and hydrogen element,respectively, and X is at least one element of O, N, S and F.

In one embodiment, ARC 16 is produced by a vapor or liquid phasedeposition (such as, for example, CVD, PECVD, PVD, ALD and spin-oncoating) method using appropriate precursors or combination ofprecursors containing elements described above.

In some embodiments, ARC 16 is a Si:C:H:X film. These Si containingfilms are deposited from at least one Si containing precursor. Moreparticularly, the Si:C:H:X films are deposited from at least one Sicontaining precursor with, or without, additions of nitrogen and/oroxygen and/or fluorine and/or sulfur containing precursors. The Sicontaining precursor that is employed can comprise any Si containingcompound including molecules selected from silane (SiH₄) derivativeshaving the molecular formula SiR₄, cyclic Si containing compoundsincluding cyclocarbosilane where the R substitutents may or may not beidentical and are selected from H, alkyl, phenyl, vinyl, allyl, alkenylor alkynyl groups that may be linear, branched, cyclic, polycyclic andmay be functionalized with nitrogen containing substituents, any cyclicSi containing compounds including cyclosilanes, and cyclocarbosilanes.

Preferred Si precursors include, but are not limited to, silane,methylsilane, dimethylsilane, trimethylsilane, tetramethylsilane,ethylsilane, diethylsilane, triethylsilane, tetraethylsilane,ethylmethylsilane, triethylmethylsilane, ethyldimethylsilane,ethyltrimethylsilane, diethyldimethylsilane,1,1,3,3,-tetrahydrido-1,3-disilacyclobutane; 1,3-disilacyclobutane;1,3-dimethyl-1,3-dihydrido-1,3-disilylcyclobutane; 1,1,3,3,tetramethyl-1,3-disilacyclobutane;1,1,3,3,5,5-hexahydrido-1,3,5-trisilane;1,1,3,3,5,5-hexamethyl-1,3,5-trisilane;1,1,1,4,4,4,-hexahydrido-1,4-disilabutane; and 1,4-bis-trihydrosilylbenzene. Also the corresponding meta substituted isomers, such asdimethyl-1-propyl-3-silabutane; 2-silapropane, 1,3-disilacyclobutane,1,3-disilapropane, 1,5-disilapentane, or 1,4-bis-trihydrosilyl benzenecan be employed.

A single precursor such as silane amine, Si(Net)₄, can be used as thesilicon, carbon and nitrogen source. Another preferred method is amixture of precursors, a Si containing source such as silane, disilane,or a alkylsilane such as tetramethylsilane, or trimethylsilane, and anitrogen containing source such as ammonia, amines, nitriles, aminos,azidos, azos, and hydrizos. An additional carbon source and/or carbonand nitrogen containing source comprised of a linear, branched, cyclicor polycyclic hydrocarbon backbone of —[CH₂]_(n)—, where n is greaterthan or equal to 1, and may be substituted by functional groups selectedfrom alkenes (—C═C—), alkynes (—C≡C—), amines (—C—N—), nitriles (—C≡N),amino (—NH₂), azido (—N═N═N—) and azo (—N═N—) may also be required. Thehydrocarbon backbone may be linear, branched, or cyclic and may includea mixture of linear branched and cyclic hydrocarbon moieties. Theseorganic groups are well known and have standard definitions that arealso well known in the art. These organic groups can be present in anyorganic compound.

In some embodiments, the method may further include the step ofproviding a parallel plate reactor, which has an area of a substratechuck from 85 cm² to 750 cm², and a gap between the substrate and a topelectrode from 1 cm to 12 cm. A high frequency RF power is applied toone of the electrodes at a frequency from 0.45 MHz to 200 MHz.Optionally, an additional RF power of lower frequency than the first RFpower can be applied to one of the electrodes. A single source precursoror a mixture of precursors which provide a silicon, carbon and nitrogensource are introduced into a reactor.

The conditions used for the deposition step may vary depending on thedesired final properties of ARC 16. Broadly, the conditions used forproviding ARC 16 that contain the elements Si:C:H:X, include: settingthe substrate temperature within a range from 100° C. to 700° C.;setting the high frequency RF power density within a range from 0.1W/cm² to 2.0 W/cm²; setting the gas flow rates within a range from 5sccm to 10000 sccm; setting the inert carrier gases, such as helium(or/and argon) flow rate within a range from 10 sccm to 10000 sccm;setting the reactor pressure within a range from 1 Torr to 10 Torr; andsetting the high frequency RF power within a range from 10 W to 1000 W.Optionally, a lower frequency power may be added to the plasma within arange from 10 W to 600 W. When the conductive area of the substratechuck is changed by a factor of X, the RF power applied to the substratechuck is also changed by a factor of X. Gas flows of silane, carbonand/or nitrogen gas precursors are flowed into the reactor at a flowrate within a range from 10 sccm to 1000 sccm. While gas precursors areused in the above example, liquid precursors may also be used for thedeposition.

The atomic % ranges for M in such ARC materials are as follows:preferably 0.1 atomic % to 95 atomic %, more preferably 0.5 atomic % to95 atomic %, most preferably 1 atomic % to 60 atomic % and most highlypreferably 5 atomic % to 50 atomic %. The atomic % ranges for C in theARC are as follows: preferably 0.1 atomic % to 95 atomic %, morepreferably 0.5 atomic % to 95 atomic %, most preferably 1 atomic % to 60atomic % and most highly preferably 5 atomic % to 50 atomic %. Theatomic % ranges for H in the ARC are as follows: preferably 0.1 atomic %to 50 atomic %, more preferably 0.5 atomic % to 50 atomic %, mostpreferably 1 atomic % to 40 atomic % and most highly preferably 5 atomic% to 30 atomic %. The atomic % ranges for X in the ARC are as follows:preferably O atomic % to 70 atomic %, more preferably 0.5 atomic % to 70atomic %, most preferably 1 atomic % to 40 atomic % and most highlypreferably 5 atomic % to 30 atomic %.

ARC 16 including elements of M, C and H may have a tunable index ofrefraction and extinction coefficient which can be optionally gradedalong the film thickness to match the optical properties of thesubstrate and the photoresist to be formed directly on it. Thus, theoptical properties and the lithographic features of the ARC 16 aresuperior to those obtained by a conventional single layer ARC. The ARC'soptical constants are defined here as the index of refraction n and theextinction coefficient k.

ARC 16 including elements of M, C and H can be deposited also in aparallel plate PECVD reactor with the substrate positioned on thegrounded electrode. In some embodiments, the ARC 16 can be deposited ata substrate temperature up to 400° C., and in a high-density plasma typereactor under suitable chosen conditions. It should be noted that bychanging process parameters such as bias voltage, gas mixture, gas flow,pressure and deposition temperature, the film's optical constants can bechanged. In addition, the composition of the starting precursor as wellas the introduction of oxygen, nitrogen, fluorine, and sulfur containingprecursors also allows the tunability of these films.

In another embodiment, the ARC 16 that is employed is formed by a liquiddeposition process including, for example, spin-on coating, spraycoating, dip coating, brush coating, evaporation or chemical solutiondeposition. The ARC formed by liquid deposition comprises a polymer thathas at least one monomer unit comprising the formula M-R^(A) wherein Mis at least one of the elements of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf andLa and R^(A) is a chromophore. Such an ARC is described in U.S. PatentPublication No. 2009/0081418 the entire content of which is incorporatedherein by reference. In some embodiments, M within the monomer unit mayalso be bonded to organic ligands including elements of C and H, across-linking component, another chromophore or mixtures thereof. Theorganic ligands may further include one of the elements of O, N, S andF. When the organic ligand is bonded to M, it is bonded to M′ through C,O, N, S, or F.

In other embodiments, the ARC 16 formed by liquid deposition may alsoinclude at least one second monomer unit, in addition to the at leastone monomer unit represented by the formula M-R^(A). When present, theat least one second monomer unit has the formula M′, —R^(B), wherein M′is at least one of the elements of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf andLa, and R^(B) is a cross-linking agent. M and M′ may be the same ordifferent elements. In these two formulae, M and M′ within the monomerunit may be also be bonded to organic ligands including atoms of C andH, a cross-linking component, a chromophore or mixtures thereof. Theorganic ligands may further include one of the elements of O, N, S andF. When the organic ligand is bonded to M and M′, it is bonded to M orM′ through C, O, N, S, or F.

The liquid ARC composition comprising M-R^(A) or M-R^(A) and M′—R^(B)may also comprise at least one additional component, including aseparate crosslinker, an acid generator or a solvent. When liquiddeposition is employed, the ARC is formed by liquid phase deposition ofa liquid composition that includes an inorganic precursor that includeselement of M, C and H, wherein M is at least one of the elements of Si,Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La. The inorganic precursor used informing the ARC may optionally include elements of O, N, S, F ormixtures thereof. In some embodiments, M is preferably Si. The liquidcomposition also includes, in addition to the inorganic precursor, achromophore, a cross-linking component, an acid generator and solvent.

One embodiment of an inorganic ARC composition used in the liquiddeposition embodiment comprises M-R^(A) and M′—R^(B) units, wherein Mand M′ are at least one of the elements of Si, Ge, B, Sn, Fe, Ta, Ti,Ni, Hf and La or are selected from Group IIIB to Group VIB, Group IIIA,and Group IVA. The inorganic precursor used in forming the ARC mayoptionally include elements of O, N, S, F or mixtures thereof. Oneembodiment of the ARC composition comprises the MO_(y) unit which can beany one of many different metal-oxide forms. An exemplary list of suchmetal-oxide forms for a particular metal is as follows: MO₃; wherein Mis Sc, Y, lanthanide, and Group IIIA; B, Al, Ga or In; MO₄; wherein M isGroup IVB; Ti, Zr or Hf, and Group IVA; Sn or Ge; MO₅; wherein M isGroup VB; V, Nb or Ta; or P. The Group VB metals are also known to formstable metal oxo forms, LMO₃, wherein L is an oxo; LMO; many of thelisted metals form stable acetoacetato-metal complexes; LMO; many of thelisted metals form stable cyclopentadienyl-metal complexes; LMO; whereinL is an alkoxy ligand; M is Sc, Y, or lanthanide, Group IVB, and GroupVB; or LMO; wherein L is an alkyl or phenyl ligand; M is Group IIIA orGroup IVA.

The chromophore, cross-linking component and acid generator that can beused in the liquid deposited ARC are defined in greater detail withrespect to the following embodiment. In one embodiment, the ARC 16formed by liquid deposition is characterized by the presence of asilicon-containing polymer having units selected from a siloxane,silane, carbosilane, oxycarbosilane, silsesquioxane,alkyltrialkoxysilane, tetra-alkoxysilane, or silicon-containing andpendant chromophore moieties. The polymer containing these units may bea polymer containing these units in the polymer backbone and/or inpendant groups. Preferably, the polymer contains the preferred units inits backbone. The polymer is preferably a polymer, a copolymer, a blendincluding at least two of any combination of polymers and/or copolymers,wherein the polymers include one monomer and the copolymers include atleast two monomers and wherein the monomers of the polymers and themonomers of the copolymers are selected from a siloxane, silane,carbosilane, oxycarbosilane, silsesquioxane, alkyltrialkoxysilane,tetra-alkoxysilane, unsaturated alkyl substituted silsesquioxane,unsaturated alkyl substituted siloxane, unsaturated alkyl substitutedsilane, an unsaturated alkyl substituted carbosilane, unsaturated alkylsubstituted oxycarbosilane, carbosilane substituted silsesquioxane,carbosilane substituted siloxane, carbosilane substituted silane,carbosilane substituted carbosilane, carbosilane substitutedoxycarbosilane, oxycarbosilane substituted silsesquioxane,oxycarbosilane substituted siloxane, oxycarbosilane substituted silane,oxycarbosilane substituted carbosilane, and oxycarbosilane substitutedoxycarbosilane.

The polymer should be soluble to form a solution and have film-formingcharacteristics conducive to forming ARC 16 by conventionalspin-coating. In addition to the chromophore moieties discussed below,the silicon-containing polymer also preferably contains a plurality ofreactive sites distributed along the polymer for reaction with thecross-linking component.

Examples of suitable polymers include polymers having the silsesquioxane(ladder, caged, or network) structure. Such polymers preferably containmonomers having structures (I) and (II) below:

where R_(C) comprises a chromophore and R^(D) comprises a reactive sitefor reaction with the cross-linking component.

Alternatively, general linear organosiloxane polymers containingmonomers (I) and (II) can also be used. In some cases, the polymercontains various combinations of monomers (I) and (II) including linearstructures such that the average structure for R^(C)-containing monomersmay be represented as structure (III) below and the average structurefor R^(D)-containing monomers may be represented by structure (IV)below:

where x is from 1 to 1.5. In theory, x may be greater than 1.5, however,such compositions generally do not possess characteristics suitable forspin-coating processes (e.g., they form undesirable gel or precipitatephases).

Generally, silsesquioxane polymers are preferred. If the ordinaryorganosiloxane polymers are used (e.g., monomers of linear structures(I) and (III)), then preferably, the degree of cross-linking isincreased compared to formulations based on silsesquioxanes.

The chromophore-containing groups R^(C) (or R^(A) in the genericdescription above) may contain any suitable chromophore which (i) can begrafted onto the silicon-containing polymer (or M moiety of the genericmonomer defined above) (ii) has suitable radiation absorptioncharacteristics at the imaging wavelength, and (iii) does not adverselyaffect the performance of the layer or any overlying layers.

Preferred chromophore moieties include benzene and its derivatives,chrysenes, pyrenes, fluoranthrenes, anthrones, benzophenones,thioxanthones, and anthracenes. Anthracene derivatives, such as thosedescribed in U.S. Pat. No. 4,371,605 may also be used; the disclosure ofthis patent is incorporated herein by reference. In one embodiment,phenol, hydroxystyrene, and 9-anthracene methanol are preferredchromophores. The chromophore moiety preferably does not containnitrogen, except for possibly deactivated amino nitrogen such as inphenol thiazine.

The chromophore moieties may be chemically attached by acid-catalyzedO-alkylation or C-alkylation such as by Friedel-Crafts alkylation. Thechromophore moieties may also be chemically attached by hydrosilylationof SiH bond on the parent polymer. Alternatively, the chromophore moietymay be attached by an esterification mechanism. A preferred acid forFriedel-Crafts catalysis is HCl.

Preferably, 15 to 40% of the functional groups contain chromophoremoieties. In some instances, it may be possible to bond the chromophoreto the monomer before formation of the silicon-containing polymer. Thesite for attachment of the chromophore is preferably an aromatic groupsuch as a hydroxybenzyl or hydroxymethylbenzyl group. Alternatively, thechromophore may be attached by reaction with other moieties such ascyclohexanol or other alcohols. The reaction to attach the chromophoreis preferably an esterification of the alcoholic OH group.

R^(D) (or R^(B) in the generic description above) comprises a reactivesite for reaction with a cross-linking component. Preferred reactivemoieties contained in R^(D) are alcohols, more preferably aromaticalcohols (e.g., hydroxybenzyl, phenol, hydroxymethylbenzyl, etc.) orcycloaliphatic alcohols (e.g., cyclohexanoyl). Alternatively, non-cyclicalcohols such as fluorocarbon alcohols, aliphatic alcohols, aminogroups, vinyl ethers, and epoxides may be used.

Preferably, the silicon-containing polymer (before attachment of thechromophore) of a liquid deposited ARC ispoly(4-hydroxybenzylsilsesquioxane). Examples of other silsesquioxanepolymers include: poly(p-hydroxyphenylethylsilsesquioxane),poly(p-hydroxyphenylethylsilsesquioxane-co-p-hydroxy-alpha-methylbenzylsilsesquioxane),poly(p-hydroxyphenylethylsilsesquioxane-co-methoxybenzylsilsesquioxane),poly(p-hydroxyphenylethylsilsesquioxane-co-t-butylsilsesquioxane),poly(p-hydroxyphenylethylsilsesquioxane-co-cyclohexylsilsesquioxane),poly(p-hydroxyphenylethylsilsesquioxane-co-phenylsilsesquioxane),poly(p-hydroxyphenylethylsilsesquioxane-co-bicycloheptylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-p-hydroxybenzylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-methoxybenzylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-t-butylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-cyclohexylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-phenylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-bicycloheptylsilsesquioxane),poly(p-hydroxybenzylsilsesquioxane-co-p-hydroxyphenylethylsilsesquioxane),andpoly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-alpha-methylbenzylsilsesquioxane).

The Si containing polymers that can be used in a liquid deposited ARCpreferably have a weight average molecular weight, before reaction withthe cross-linking component, of at least 1000, more preferably a weightaverage molecular weight of 1000-10000.

The cross-linking component of the liquid deposited ARC is preferably acrosslinker that can be reacted with an SiO containing polymer in amanner which is catalyzed by generated acid and/or by heating. Thiscross-linking component can be inorganic or organic in nature. It can bea small compound (as compared with a polymer or copolymer) or a polymer,a copolymer, or a blend including at least two of any combination ofpolymers and/or copolymers, wherein the polymers include one monomer andthe copolymers include at least two monomers. Generally, thecross-linking component used in the liquid deposited antireflectivecoating compositions may be any suitable cross-linking agent known inthe negative photoresist art which is otherwise compatible with theother selected components of the composition. The cross-linking agentspreferably act to crosslink the polymer component in the presence of agenerated acid. Preferred cross-linking agents are glycoluril compoundssuch as tetramethoxymethyl glycoluril, methylpropyltetramethoxymethylglycoluril, and methylphenyltetramethoxymethyl glycoluril, availableunder the POWDERLINK trademark from American Cyanamid Company. Otherpossible cross-linking agents include: 2,6-bis(hydroxymethyl)-p-cresol,compounds having the following structures:

including their analogs and derivatives, such as those found in JapaneseLaid-Open Patent Application (Kokai) No. 1-293339, as well as etherifiedamino resins, for example methylated or butylated melamine resins(N-methoxymethyl- or N-butoxymethyl-melamine respectively) ormethylated/butylated glycolurils, for example as can be found inCanadian Patent No. 1 204 547. Other cross-linking agents such asbis-epoxies or bis-phenols (e.g., bisphenol-A) may also be used.Combinations of cross-linking agents may be used. The cross-linkingcomponent may be chemically bonded to the Si containing polymerbackbone.

In another embodiment, the cross-linking component is asilicon-containing polymer having at least one unit selected from asiloxane, silane, carbosilane, oxycarbosilane, silsesquioxane,alkyltrialkoxysilane, and tetra-alkoxysilane. The polymer is preferablya polymer, a copolymer, a blend including at least two of anycombination of polymers and/or copolymers, wherein the polymers includeone monomer and the copolymers include at least two monomers and whereinthe monomers of the polymers and the monomers of the copolymers areselected from a siloxane, silane, carbosilane, oxycarbosilane,silsesquioxane, alkyltrialkoxysilane, tetra-alkoxysilane, unsaturatedalkyl substituted silsesquioxane, unsaturated alkyl substitutedsiloxane, unsaturated alkyl substituted silane, an unsaturated alkylsubstituted carbosilane, unsaturated alkyl substituted oxycarbosilane,carbosilane substituted silsesquioxane, carbosilane substitutedsiloxane, carbosilane substituted silane, carbosilane substitutedcarbosilane, carbosilane substituted oxycarbosilane, oxycarbosilanesubstituted silsesquioxane, oxycarbosilane substituted siloxane,oxycarbosilane substituted silane, oxycarbosilane substitutedcarbosilane, and oxycarbosilane substituted oxycarbosilane.

The acid generator used in the liquid deposited ARC composition ispreferably an acid generator compound that liberates acid upon thermaltreatment. A variety of known thermal acid generators are suitablyemployed such as, for example, 2,4,4,6-tetrabromocyclohexadienone,benzoin tosylate, 2-nitrobenzyl tosylate and other alkyl esters oforganic sulfonic acids, blocked alkyl phosphoric acids, blockedperfluoroalkyl sulfonic acids, alkyl phosphoric acid/amine complexes,perfluoroalkyl acid quats wherein the blocking can be by covalent bonds,amine and quaternary ammonium. Compounds that generate a sulfonic acidupon activation are generally suitable. Other suitable thermallyactivated acid generators are described in U.S. Pat. Nos. 5,886,102 and5,939,236; the disclosures of these two patents are incorporated hereinby reference. If desired, a radiation-sensitive acid generator may beemployed as an alternative to a thermally activated acid generator or incombination with a thermally activated acid generator. Examples ofsuitable radiation-sensitive acid generators are described in U.S. Pat.Nos. 5,886,102 and 5,939,236. Other radiation-sensitive acid generatorsknown in the resist art may also be used as long as they are compatiblewith the other components of the antireflective composition. Where aradiation-sensitive acid generator is used, the cure (cross-linking)temperature of the composition may be reduced by application ofappropriate radiation to induce acid generation which in turn catalyzesthe cross-linking reaction. Even if a radiation-sensitive acid generatoris used, it is preferred to thermally treat the composition toaccelerate the cross-linking process (e.g., for wafers in a productionline).

The antireflective coating compositions used in the liquid depositionprocess preferably contain (on a solids basis) in a suitable solventcommonly known to those skilled in the art (i) from 10 wt % to 98 wt. %of a polymer including M, more preferably from 70 wt. % to 80 wt. %,(ii) from 1 wt % to 80 wt. % of cross-linking component, more preferablyfrom 3 wt. % to 25%, most preferably from 5 wt. % to 25 wt. %, and (iii)from 1 wt. % to 20 wt. % acid generator, more preferably 1 wt. % to 15wt. %.

After liquid depositing the ARC 16, a post deposition baking step istypically, but not necessarily always, used to remove unwantedcomponents, such as solvent, and to effect crosslinking. When performed,the baking step is conducted at a temperature from 60° C. to 400° C.,with a baking temperature from 80° C. to 300° C. being even morepreferred. The duration of the baking step varies and is not critical tothe practice of the present disclosure. The baked and previously liquiddeposited ARC may further undergo a post curing treatment process. Thispost curing treatment may include one of the post treatments used abovefor the optional dielectric cap. As such, the various post treatmentsand conditions used above in treating the optional dielectric cap areincorporated herein by reference.

In addition, the composition of the starting precursor used in liquiddeposition as well as the introduction of oxygen, nitrogen, fluorinecontaining precursors also allows the tunability of these films. Ineither embodiment mentioned above, the ARC's optical constants aredefined here as the index of refraction n and the extinction coefficientk. In general, the ARC 16 can be modeled so as to find optimum opticalparameters (n and k values) of ARC as well as optimum thickness. Thepreferred optical constants of the ARC are in the range from n=1.4 ton=2.6 and k=0.01 to k=0.78 at a wavelength of 248, 193 and 157, 126 nmand extreme ultraviolet (13.4 nm) radiation.

In addition to the above, the ARC 16 in any embodiment has good etchselectivity during pattern transfer. Etch selectivities of 1.5-4 to 1 ofthe ARC 16 to cured dielectric materials can be obtained. Furthermore,the use of the ARC 16 as described above (vapor or liquid deposited)maintains the pattern and structural integrity after curing of thepatterned dielectric materials. This is critical as the ARC 16 isretained as a permanent part of the final interconnect stack.

In some embodiments, the optional dielectric cap 14 and the ARC 16 canbe combined into a graded cap that includes properties of both adielectric cap layer and an ARC. Such a graded cap includes at least alower region that includes elements of a dielectric cap and an upperregion that includes elements of an ARC. The graded cap can be formedutilizing any of the methods mentioned above in forming the dielectriccap and/or ARC.

Referring now to FIG. 2, there is illustrated the initial structure 10of FIG. 1 after forming a photoresist 18 on an upper surface of theinitial structure. In the particular embodiment illustrated, thephotoresist 18 is formed directly on an upper surface of ARC 16.Photoresist 18 can include any conventional chemically amplifiedphotoresist material that is well known to one skilled in the art.Photoresist 18 may be a negative-tone photoresist material or apositive-tone photoresist material. These chemically amplifiedphotoresists generate a strong acid to catalyze the deproetection or thecros slinking of the photoresist polymer after exposure to anirradiation source and baking. This photo-generated acid will beemployed herein to form self-aligned sidewall patterns of permanentpatterned dielectric structures.

The photoresist 18 (negative-tone or positive-tone) that is employed ispresent in a composition that includes, in addition to the photoresistmaterial, a photoacid generator, a base additive and a solvent. When thephotoresist 18 is a negative-tone photoresist material, it may be formedfrom a composition optionally including an additional cross-linker. By“negative-tone” it is meant that the part of the photoresist that isexposed to an actinic irradiation will not be removed by a conventionaldeveloper, while the unexposed part of the photoresist is removed. Whenthe photoresist 18 is a positive-tone photoresist material, it is formedfrom a composition that includes a photoresist material that contains atleast photo/acid imageable functional groups to form positive-tonepatterns, a photoacid generator, a base additive and a solvent. By‘positive-tone” it is meant that the part of the photoresist that isexposed to an actinic irradiation will be removed by a conventionaldeveloper, while the unexposed part of the photoresist is not removed.The photoacid generators, base additives and solvents are well known tothose skilled in the art and, as such, details regarding thosecomponents are not fully provided.

The photoresist 18 is typically applied to an upper most surface of theinitial structure 10 utilizing a conventional deposition processincluding, but not limited to, spin-on coating, dip coating, brushing,evaporation, blade coating, ink jet dispensing, chemical vapordeposition, and plasma enhanced chemical vapor deposition. In someembodiments, the as-deposited photoresist 18 can be subjected to a postdeposition baking step to remove any unwanted components such as solventfrom the applied photoresist. When such a post deposition baking step isemployed, the post deposition baking step is performed at a temperaturefrom 40° C. to 200° C., with a temperature from 60° C. to 140° C. beingmore typical. The duration of the post deposition baking step variesfrom 10 seconds to 600 seconds and is not critical herein.

The thickness of photoresist 18 may vary depending on the type ofphotoresist material employed as well as the type of deposition processthat is used in forming the same. Typically, photoresist 18 has athickness from 1 nm to 50000 nm, with a thickness from 10 nm to 5000 nmbeing more typical.

Referring now to FIG. 3, there is illustrated the structure of FIG. 2after patterning the photoresist 18 to form latent images of a desiredcircuitry. In FIG. 3, reference numeral 18′ is used to denote thepatterned photoresist, and reference numeral 20 is used to denote the atleast one opening (i.e., interconnect pattern) that is formed by thispattern-wise exposure step. An optional post-exposure baking step may berequired to effect a desired photochemical reaction. When performed, thepost-exposure baking step is conducted at a temperature from 60° C. to200° C., with a post-exposure baking temperature from 80° C. to 140° C.being more typical. The duration of the post-exposure baking step variesand is not critical herein. After exposure and post-exposure baking, thelatent images are developed into the relief images with an appropriatedeveloper, usually an aqueous base solution, such as 0.26Ntetramethylammoniahydroxide (TMAH) solution.

The pattern wise exposing process can be accomplished in a variety ofways, including, for example, through a mask with a lithography stepperor a scanner with an exposure light source of G-line, Mine (365 nm), DUV(248 nm, 193 nm, 157 nm, 126 nm), Extreme UV (13.4 nm, 6.7 nm), anelectron beam, or an ion beam. The exposing process may be performed ina dry mode or an immersion mode. The pattern-wise exposing process alsoincludes direct writing without the use of a mask with, for example,light, electron beam, ion beam, and scanning probe lithography.

As stated above and as illustrated in FIG. 3, the patterned photoresist18′ includes at least one opening 20 therein. As shown, the at least oneopening 20 exposes an upper surface, e.g., the ARC 16, of the initialstructure 10.

As stated previously, the exposure of the chemically amplifiedphotoresist and subsequent baking generate a strong acid from thephotoacid generator of the photoresist composition. The residual acid onthe sidewall of the photoresist patterns can catalyze cros slinking ofthe dielectric coating material to be applied later on.

In some embodiments of the present disclosure, a thin protective layer(not shown) can be formed atop the patterned photoresist. This thinprotective layer functions to protect the pattern, the size, the shapeand other features of the patterned photoresist during the subsequentsteps of applying the dielectric coating material. When present theprotective layer can be formed utilizing a conventional depositionprocess such as, for example, spin coating, dip coating, spray coating,chemical vapor deposition, plasma enhanced chemical vapor deposition,chemical solution deposition, or evaporation. The thickness of theprotective layer is typically 1/10000 to ⅕ the width of the opening ofthe photoresist pattern, with a thickness from 1/1000 to 1/10 the widthof the opening of the photoresist pattern being more typical

In other embodiments, a thin protective layer (not shown) is formed atopthe photoresist pattern by treatment of the photoresist pattern. Thissurface treatment of the photoresist pattern can be irradiation to anelectromagnetic wave, such as a UV light source of a wavelength shorterthan 200 nm, plasma treatment or chemical treatment from a vapor or aliquid phase. This surface treatment serves to harden at least the uppersurface of the patterned photoresist.

Referring now to FIG. 4, there is illustrated the structure of FIG. 3after forming dielectric sidewall structures 22 within the at least oneopening 20 and on sidewalls of the patterned photoresist 18′. Thedielectric sidewall structures 22 are formed by first overfilling the atleast one opening 20 with a dielectric coating material. The dielectriccoating material that can be employed includes any dielectric materialthat can be crosslinked with an acid and form a dielectric material uponsubsequent curing. More particularly, the dielectric coating materialcomprises a polymer, copolymer, or blend of polymers and/or copolymershaving at least one reactive group. The thickness of the dielectriccoating may vary depending on the requirement of the chip and thetechnique used to form the same as well as the material make-up of thelayer. Typically, the dielectric coating material has a thickness thatis greater than the thickness of the patterned photoresist 18′. Thedielectric coating material can be formed by any conventional depositionprocess including, for example, those mentioned above for formingphotoresist 18.

The cured product of the dielectric coating material can serve as anpermanent on-chip dielectric insulator. The dielectric coating materialemployed herein can be deposited from a liquid phase. In the presentdisclosure, the terms “cure” or “curing” are used interchangeable torefer to one of the processes selected from a thermal cure, an electronbeam cure, an ultra-violet (UV) cure, an ion beam cure, a plasma cure, amicrowave cure or a combination thereof. A “cured” product of thedielectric coating material is the product of the dielectric coatingmaterial after it has undergone one of the aforementioned cureprocesses. The “cured” product of a dielectric coating material isdifferent from the originally deposited dielectric coating material inchemical nature and physical, mechanical and electrical properties.

The dielectric coating material that can be employed includes afunctionalized polymer, copolymer or blend including at least two of anycombination of polymers and/or copolymers having one or moreacid-sensitive imageable groups. After curing, the dielectric coatingmaterial is converted into a permanent on-chip dielectric materialhaving a dielectric constant of about 7 or less. It is noted that whenthe dielectric coating material is comprised of a polymer, the polymerincludes at least one monomer (to be described in greater detail below).When the dielectric coating material is comprised of a copolymer, thecopolymer includes at least two monomers (to be described in greaterdetail below). The blends of polymers and/or copolymers include at leasttwo of any combination of polymers and/or copolymers described below.

In general terms, the dielectric coating material is a compositionincluding a polymer, a copolymer, or a blend including at least two ofany combination of acid-sensitive polymers and/or copolymers, whereinthe polymers include one monomer and the copolymers include at least twomonomers and wherein the monomers of the polymers and the monomers ofthe copolymers are selected from a siloxane, silane, carbosilane,oxycarbosilane, silsesquioxane, alkyltrialkoxysilane,tetra-alkoxysilane, unsaturated alkyl substituted silsesquioxane,unsaturated alkyl substituted siloxane, unsaturated alkyl substitutedsilane, an unsaturated alkyl substituted carbosilane, unsaturated alkylsubstituted oxycarbosilane, carbosilane substituted silsesquioxane,carbosilane substituted siloxane, carbosilane substituted silane,carbosilane substituted carbosilane, carbosilane substitutedoxycarbosilane, oxycarbosilane substituted silsesquioxane,oxycarbosilane substituted siloxane, oxycarbosilane substituted silane,oxycarbosilane substituted carbosilane, and oxycarbosilane substitutedoxycarbosilane.

More specifically, the dielectric coating material that can be employedis a composition comprising an acid-sensitive polymer of one monomer ora copolymer of at least two monomers selected from siloxane, silane,carbosilane, oxycarbosilane, organosilicates, silsesquioxanes and thelike. The dielectric coating material may also be a compositioncomprising a polymer of one monomer or a copolymer of at least twomonomers selected from alkyltrialkoxysilane, tetra-alkoxysilane,unsaturated alkyl (such as vinyl) substituted silsesquioxane,unsaturated alkyl substituted siloxane, unsaturated alkyl substitutedsilane, an unsaturated alkyl substituted carbosilane, unsaturated alkylsubstituted oxycarbosilane, carbosilane substituted silsesquioxane,carbosilane substituted siloxane, carbosilane substituted silane,carbosilane substituted carbosilane, carbosilane substitutedoxycarbosilane, oxycarbosilane substituted silsesquioxane,oxycarbosilane substituted siloxane, oxycarbosilane substituted silane,oxycarbosilane substituted carbosilane, and oxycarbosilane substitutedoxycarbosilane. Additionally, the dielectric coating material maycomprise a blend including at least two of any combination ofacid-sensitive polymers and/or copolymers, wherein the said polymersinclude one monomer and the said copolymers include at least twomonomers and wherein the monomers of the said polymers and the monomersof the said copolymers are selected from a siloxane, silane,carbosilane, oxycarbosilane, silsesquioxane, alkyltrialkoxysilane,tetra-alkoxysilane, unsaturated alkyl substituted silsesquioxane,unsaturated alkyl substituted siloxane, unsaturated alkyl substitutedsilane, an unsaturated alkyl substituted carbosilane, unsaturated alkylsubstituted oxycarbosilane, carbosilane substituted silsesquioxane,carbosilane substituted siloxane, carbosilane substituted silane,carbosilane substituted carbosilane, carbosilane substitutedoxycarbosilane, oxycarbosilane substituted silsesquioxane,oxycarbosilane substituted siloxane, oxycarbosilane substituted silane,oxycarbosilane substituted carbosilane, and oxycarbosilane substitutedoxycarbosilane.

Optionally the dielectric coating material may be a composition furthercomprising at least one microscopic pore generator (porogen). The poregenerator may be or may not be acid sensitive.

Illustrative polymers for the dielectric coating material include, butare not limited to, siloxane, silane, carbosilane, oxycarbosilane,silsesquioxane-type polymers including caged, linear, branched orcombinations thereof. In one embodiment, the dielectric coating materialis a photo-patternable low k (PPLK) composition comprising a blend ofthese photo/acid-sensitive polymers. Examples of PPLK materials that canbe employed in this application are disclosed, for example, in U.S. Pat.Nos. 7,041,748, 7,056,840, and 6,087,064, as well as U.S. PatentApplication Publication No. 2008/0286467, U.S. Patent ApplicationPublication No. 2009/0233226, U.S. Patent Application Publication No.2009/0291389, U.S. patent application Ser. No. 12/569,200, filed Sep.29, 2009 all of which are incorporated herein by reference in theirentirety. When a PLLK material is employed as the dielectric coatingmaterial, a protective layer is typically present atop the patternedphotoresist, or the patterned photoresist has a surface region that ishardened.

The dielectric coating material is formed from a composition thatincludes at least one of the above mentioned polymers, copolymers orblends and a solvent that is typically compatible with the underlyingphotoresist patterns. By “compatible with”, it is meant that theapplication of the dielectric coating material composition directly overthe photoresist patterns does not substantially alter the size, theshape, and other features of the photoresist patterns. This solvent maybe hydrocarbon, alcohol, water or a mixture thereof. In someembodiments, the dielectric coating material may be formed from acomposition that optionally includes an additional cross-linker.

The additional cross-linker can be a small compound (as compared with apolymer or copolymer) or a polymer, a copolymer, or a blend including atleast two of any combination of polymers and/or copolymers, wherein thepolymers include one monomer and the copolymers include at least twomonomers and wherein the monomers of the polymers and the monomers ofthe copolymers are selected from a siloxane, silane, carbosilane,oxycarbosilane, silsesquioxane, alkyltrialkoxysilane,tetra-alkoxysilane, unsaturated alkyl substituted silsesquioxane,unsaturated alkyl substituted siloxane, unsaturated alkyl substitutedsilane, an unsaturated alkyl substituted carbosilane, unsaturated alkylsubstituted oxycarbosilane, carbosilane substituted silsesquioxane,carbosilane substituted siloxane, carbosilane substituted silane,carbosilane substituted carbosilane, carbosilane substitutedoxycarbosilane, oxycarbosilane substituted silsesquioxane,oxycarbosilane substituted siloxane, oxycarbosilane substituted silane,oxycarbosilane substituted carbosilane, and oxycarbosilane substitutedoxycarbosilane.

The solvents that are used in the dielectric coating materialcomposition that are compatible with the underlying photoresist patternsinclude organic solvents such as hydrocarbons and alcohols, and water ora mixture thereof.

When the solvent of the dielectric composition is not compatible withthe photoresist pattern, a thin protective layer may be formed on thesurface of the photoresist pattern as described previously to maintainthe pattern integrity of the photoresist pattern.

The dielectric coating material can be formed utilizing a depositionprocess including, for example, spin-on-coating, dip coating, spraycoating, brush coating, blade coating, and ink-jet dispensing. Afterapplying the dielectric coating material a post deposition baking stepis typically, but not necessarily always, required to remove unwantedcomponents, such as solvent. When performed, the baking step can beconducted at a temperature from 40° C. to 200° C., with a bakingtemperature from 60° C. to 140° C. being more typical. The duration ofthe baking step varies from 10 seconds to 600 seconds and is notcritical herein.

After overfilling the at least one opening 20 with the dielectriccoating material, the structure is subjected to a baking step thatcauses diffusion of residual acid from the sidewalls of the patternedphotoresist 18′ into the neighboring sidewall portions of the dielectriccoating material and subsequent crosslinking with the neighboringsidewall portions of the dielectric coating material occurs. The bakingstep is performed at a temperature from 40° C. to 200° C., with atemperature from 60° C. to 140° C. being more typical. The duration ofthe baking step may vary depending on the type of dielectric coatingmaterial and photoresist employed. Typically, the duration of the bakingstep is from 1 second to 3600 second, with a duration from 30 second to180 seconds being more typical.

After the baking step, a rinsing step is performed that removes at leastportions of the dielectric coating material that are not crosslinkedproviding the dielectric sidewall structures 22 as illustrated in FIG.4. The rinsing step that can be employed includes any solvent orsolution that is capable of removing the non-crosslinked portions of thedielectric coating material relative to the crosslinked, i.e.,dielectric sidewall structures 22. Examples of solutions that can beemployed in this rinsing step include, but are not limited to, thesolvent of the dielectric composition, such as a hydrocarbon, alcohol,water or a mixture thereof. This rinsing step also removes theover-coating of the dielectric material coating on top of the patternedphotoresist.

It is observed that after forming the dielectric sidewall structures 22within the at least one opening, at least a new opening is formed with awidth narrower (herein after referred to as narrowed width opening 20′)than that of the parent opening 20 within the patterned photoresist. SeeFIG. 4 as well. The at least one narrowed width opening 20′ has a widththat is less than the width of the original at least one opening 20.Typically, the at least one narrowed width opening 22′ has a width from99.9% to 1.0% of the width of the parent opening 20, with a width from70% to 30% being more typical. The size of the narrowed width opening20′ can be the same as or different from the size of the photoresistpattern 18′. In some embodiments of the present disclosure, the width ofeach narrowed width opening 20′ is the same. In other embodiments of thepresent disclosure, the width of the narrowed width openings can bedifferent. The width of each narrowed width opening 20′ that is formeddepends on the width of the dielectric sidewall structures formed.

After providing the dielectric sidewall structures 22 as shown in FIG.4, the patterned photoresist 18′ is removed from the structure utilizingany conventional stripping process including, for example, ashing. Inanother embodiment, the patterned photoresist 18′ is removed by blanketexposure to irradiation and baking, followed by developing with aphotoresist developer, such as TMAH. The removal of the patternedphotoresist 18′ provides additional second openings 21 betweenneighboring dielectric sidewall structures 22. The width of theadditional second openings 21, which is dependent on the width of thepatterned photoresist 18′, can be the same or different as that of thenarrowed width opening 20′. See FIG. 5.

In some embodiments and prior to curing the dielectric sidewallstructures, it is possible to open the underlying exposed portions ofthe ARC 16 and the optional dielectric cap 14 and then fill the narrowedwidth opening with at least one electrically conductive material. Thisparticular embodiment is not however shown in the drawings of thepresent disclosure. Also, the details concerning the opening of the ARC16 and the optional dielectric cap 14 and the filling of the variousopenings with at least one electrically conductive material are the sameas described herein below for the specific embodiment illustrated withinthe drawings of the present application.

Referring to FIG. 5, there is illustrated the structure that is formedafter removing the patterned photoresist 18′ and converting thedielectric sidewall structures 22 into permanent patterned dielectricstructures 22′ (e.g., self-aligned double patterned permanent dielectricstructures). The removal of the patterned photoresist has been describedabove. The converting of the dielectric sidewall structures 22 intopermanent patterned dielectric structures 22′ is performed by a curingprocess including, for example, a thermal cure, an electron beam cure,an ultra-violet (UV) cure, an ion beam cure, a plasma cure, a microwavecure or a combination thereof. The conditions for each of the curingprocesses are well known to those skilled in the art and any conditioncan be chosen as long as it coverts the dielectric sidewall structuresinto a permanent on-chip dielectric and maintains pattern fidelity.

In one embodiment, an irradiation cure step is performed by acombination of a thermal cure and an ultra-violet (UV) cure wherein thewavelength of the ultra-violet (UV) light is from 50 nm to 300 nm andthe light source for the ultra-violet (UV) cure is a UV lamp, an excimer(exciplex) laser or a combination thereof.

The excimer laser may be generated from at least one of the excimersselected from the group consisting of Ar₂*, Kr₂*, F₂, Xe₂*, ArF, KrF,XeBr, XeCl, XeCl, XeF, CaF₂, KrCl, and Cl₂ wherein the wavelength of theexcimer laser is in the range from 50 nm to 300 nm. Additionally, thelight of the ultra-violet (UV) cure may be enhanced and/or diffused witha lens or other optical diffusing device known to those skilled in theart.

In one embodiment, this post patterning cure is a combined UV/thermalcure. This combined UV/thermal cure is carried on a UV/thermal curemodule under vacuum or inert atmosphere, such as N₂, He and Ar.Typically, the UV/thermal cure temperature is from 100° C. to 500° C.,with a cure temperature from 300° C. to 450° C. being more typical. Theduration of the UV/thermal cure is from 0.5 min to 30 min with aduration from 1 min to 10 min being more typical. The UV cure module isdesigned to have a very low oxygen content to avoid degradation of theresultant dielectric materials.

In some embodiment, the dielectric material cure may be in different orthe same tool cluster as that used in forming the dielectric sidewallstructures 22.

Referring to FIG. 6, there is illustrated the structure that is formedafter extending the additional openings 21 and the at least one narrowedwidth opening 20′ into underling exposed portions of the ARC 16 and, ifpresent, the optional dielectric cap 14. This step of the presentdisclosure used to ‘open’ the ARC 16 and, if present, the optionaldielectric cap 14, includes any etching process such as, for example,plasma etching reactive ion etching or gas cluster ion beam etching. Theextended openings (21 and 20′) are labeled as reference numeral 23 and24, respectively, in the drawings. The extending openings 23 and 24 mayeach have the same width or different widths.

Referring now to FIG. 7, there is illustrated the structure of FIG. 6after forming at least an electrically conductive material within theextended openings 23 and 24. In some embodiments, a diffusion barrierlayer (liner) (not shown), which may comprise Ta, TaN, Ti, TiN, Ru,RuTaN, RuTa, W, WN or any other material that can serve as a barrier toprevent the electrically conductive material from diffusing through, istypically formed into the extended opening 23 prior to filling the samewith an electrically conductive material. When present the diffusionbarrier layer is formed by a deposition process such as, for example,atomic layer deposition (ALD), chemical vapor deposition (CVD), plasmaenhanced chemical vapor deposition (PECVD), physical vapor deposition(PVD), sputtering, chemical solution deposition, or plating. In someembodiments (not shown), the diffusion barrier liner may comprise acombination of layers. The thickness of the diffusion barrier liner mayvary depending on the exact means of the deposition process employed aswell as the material and number of layers employed. Typically, thediffusion barrier liner has a thickness from 4 to 40 nm, with athickness from 7 to 20 nm being more typical.

Following the formation of the diffusion barrier layer (liner), theremaining extended openings 23 and 24 are filled with an electricallyconductive material 26 forming a conductive feature. The electricallyconductive material 26 used in forming the conductive feature includes,for example, polySi, an electrically conductive metal, an alloycomprising at least one electrically conductive metal, an electricallyconductive metal silicide, an electrically conductive nanotube ornanowire, graphene or combinations thereof. Preferably, the electricallyconductive material 26 that is used in forming the conductive feature isa conductive metal such as Cu, W or Al, with Cu or a Cu alloy (such asAlCu) being highly preferred in the present invention. The electricallyconductive material 26 is filled into the remaining openings utilizing aconventional deposition process including, but not limited to CVD,PECVD, sputtering, chemical solution deposition or plating. A preferredfilling method is electrochemical plating. The size of the electricalconductive material 26 can be the same or different on this sameinterconnect level.

After deposition, a conventional planarization process such as, forexample, chemical mechanical polishing (CMP) can be used to provide astructure in which the diffusion barrier layer and the electricallyconductive material 26 each have an upper surface that is substantiallycoplanar with the upper surface of the permanent patterned dielectricstructures 22′. The resultant structure after electrically conductivematerial fill and planarization is shown, for example, in FIG. 7. It isnoted that in this embodiment, it is also possible to form differentsized conductive features within the permanent patterned dielectricstructures 22′.

After forming the structure shown in FIG. 7, another dielectric cap (notshown) can be formed on the upper surfaces of each of the permanentpatterned dielectric structures 22′ as well as atop an upper surface ofthe electrically conductive material 26. The another dielectric cap canbe formed utilizing the methods described above for optional dielectriccap 14 and the another dielectric cap can comprise the same or differentcomposition as the optional dielectric cap 14.

Reference is now made to FIGS. 8-15 which illustrate another embodimentof the present disclosure. In particular, FIGS. 8-15 represent a methodof forming a dual damascene structure. It is noted that in thisembodiment, it is also possible to form different sized conductivefeatures within a patterned dielectric material (i.e., permanentpatterned dielectric structures 22′).

This embodiment of the present disclosure begins by first providing theinitial structure 10 as shown FIG. 1. After providing the initialstructure 10, a dielectric material 50 (as shown in FIG. 8) is formed onan upper most surface of the initial structure 10. The dielectricmaterial 50 includes any interlevel or intralevel dielectric material.The dielectric material 50 that is formed on the upper most surface ofthe initial structure can have a dielectric constant about 4.3 or less,typically less than 3.8. Illustrative examples of dielectric materialsthat can be employed include, but are not limited to, silicon oxide,silsesquioxanes, C doped oxides (i.e., organosilicates) that includeatoms of Si, C, O and H, thermosetting polyarylene ethers, and dopedsilicate glass materials. The term “polyarylene” is used in thisdisclosure to denote aryl moieties or inertly substituted aryl moietieswhich are linked together by bonds, fused rings, or inert linking groupssuch as, for example, oxygen, sulfur, sulfone, sulfoxide, carbonyl andthe like.

The thickness of the dielectric material 50 may vary depending on thetype of dielectric material employed as well as the technique that wasused in forming the same. Typically, the dielectric material 50 has athickness from 5 nm to 2 μm, with a thickness from 10 nm to 500 nm beingmore typical. The dielectric material 50 can be formed utilizing anyconventional deposition process including, but not limited to, chemicalvapor deposition, plasma enhanced chemical vapor deposition,evaporation, chemical solution deposition and spin-on coating.

After providing the dielectric material 50 to the initial structure 10,the dielectric material 50 is patterned to include a plurality of firstopenings, e.g., interconnect patterns. In FIG. 9, reference numerals52L, 52 and 52R denote some of the plurality of first openings that canbe formed. Such a structure including patterned dielectric material 50′and the various first openings is shown, for example, in FIG. 9. Thepatterning of the dielectric material 50 into patterned dielectricmaterial 50′ may include a conventional lithography process (includingthe one mentioned above for patterning the photoresist 18) and etching(including dry etching and/or wet chemical etching). This patterningmethod is well known to those skilled in the art.

The plurality of first openings, e.g., 52L, 52 and 52R shown in thedrawings, can be a via opening or a trench opening. In a preferredembodiment, and as shown, each of the first openings, e.g., firstopenings 52L, 52 and 52R, is a via opening.

Referring now to FIG. 10, a photoresist 18 which is chemically amplifiedis formed on top of the patterned dielectric material 50′ and withineach of the first openings, e.g., first openings 52L, 52 and 52R. Thephotoresist 18 used in this embodiment is the same as that used forphotoresist 18 in the first embodiment.

Referring now to FIG. 11, there is shown the structure of FIG. 10 afterpatterning the photoresist 18 into a patterned photoresist 18′ havingsecond openings 53. As is illustrated, a portion of the patternedphotoresist 18′ remains in at least one of the first openings, e.g.,first opening 52 shown in FIG. 10. While some of the patternedphotoresist 18′ remains in at least one of the first openings (e.g.,first opening 52), the photoresist 18 is removed from some of the firstopenings (e.g., first openings 52L and 52R) not including the patternedphotoresist. The patterning of the photoresist 18 into a patternedphotoresist 18′ is performed utilizing the same method used in the firstembodiment. The portion of the patterned photoresist that is locatedatop the patterned dielectric material 50′ has a width that differs fromthe width of first opening 52. In one embodiment, and as illustrated,the width of the portion of the patterned photoresist 18′ atop thepatterned dielectric material 50′ is greater than the width of firstopening 52 within the patterned dielectric material 50′. In such anembodiment, the first opening 52 is a via opening, and the width of theportion of the patterned photoresist 18′ atop the patterned dielectricmaterial 50 is a width of a trench opening. In other embodiments, thefirst opening 52 is a trench opening and the width of the portion of thepatterned photoresist 18′ atop the patterned dielectric material 50′ isa width of a via opening. It is observed the second openings 53 arelocated atop and connected with first openings 52L and 52R.

Referring now to FIG. 12, there is illustrated the structure of FIG. 11after forming dielectric sidewall structures 22 on sidewalls of thepatterned photoresist 18′. The dielectric sidewall structures 22 includeone of the dielectric coating materials mentioned in the firstembodiment and the dielectric sidewall structures are also formed asdescribed above. The formation of dielectric sidewall structures 22 onsidewalls of the patterned photoresist 18′ narrows the width of eachsecond opening 53 providing narrowed width second openings 53′. The sizeof each narrowed width second opening 53′ can be the same or different.

Referring now to FIG. 13, there is shown the structure of FIG. 12 afterremoving the patterned photoresist 18′, and converting each of thedielectric sidewall structures 22 into a permanent patterned dielectricstructure 22′. The removal of the patterned photoresist 18′ and theconverting of the dielectric sidewall structures 22 to permanentpatterned dielectric structures 22′ include the same techniques asmentioned above in the first embodiment of this disclosure. This removalof the patterned photoresist 18′ also recovers the first opening 52. Theremoval of the patterned photoresist 18′ also forms a third opening 54between neighboring permanent patterned dielectric structures that isconnected to the first opening 52. In some embodiments, the convertingstep can also be used to cure the patterned dielectric material 50′ aswell. The method of removal of the patterned photoresist 18′ is the sameas the one used the first embodiment. The narrowed width second openings53′ are located atop and are in contact with the first openings 52L and52R, while the third opening 54 is located atop and is connected withthe first opening 52. The sizes of the first, the narrowed width secondand the third openings can be the same or different.

Referring now to FIG. 14, there is shown the structure of FIG. 13 afteretching exposed portions of the ARC 16 and optional dielectric cap 14.The opening of the ARC 16 and optional dielectric cap 14 is the same asthat described above in the first embodiment. In FIG. 14, referencenumerals 52L′, 52′ and 52R′ are used to denote extended first openingsthat are formed after opening the ARC 16 and the optional dielectric cap14.

Referring now to FIG. 15, there is shown the structure of FIG. 14 afterfilling each of the various openings with at least an electricallyconductive material. The processing used to fill the openings is thesame as that described in the first embodiment. In some embodiments, andprior to filling with the electrically conductive material a diffusionbarrier layer (as described above in the first embodiment) can be formedwithin the openings.

After providing the structure shown in FIG. 15, another dielectric cap(as described above in the first embodiment) can be formed atop theupper exposed surface of the structure.

It is noted that in some embodiments of the methods disclosed above, itis possible to form interconnect structures that include at least onepatterned dielectric layer (i.e., element 22′) located on a substrate(i.e., element 12), wherein said at least one patterned dielectric layer(i.e., element 22′) includes differently sized conductive features(i.e., element 26) therein embedded therein. The differently sizedconductive features are laterally adjacent each other. As such, thedifferently sized conductive features all have bottom surfaces locatedat a same horizontal level (e.g., plane) within the interconnectstructure and top surfaces that are located on a same horizontal level(e.g., plane) within the interconnect structure. In some embodiments,alternating adjacent conductive features on the same interconnect levelare of a same size.

While the present disclosure has been particularly shown and describedwith respect to preferred embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formsand details may be made without departing from the spirit and scope ofthe present disclosure. It is therefore intended that the presentdisclosure not be limited to the exact forms and details described andillustrated, but fall within the scope of the appended claims.

1. A method of fabricating a self-aligned permanent on-chip interconnectstructure comprising: forming a patterned photoresist having at leastone opening on a surface of a substrate; forming a dielectric sidewallstructure on each sidewall of said patterned photoresist and within saidat least one opening, wherein a narrowed width opening is locatedbetween neighboring dielectric sidewall structures; removing thepatterned photoresist to provide additional openings between neighboringdielectric structures; and converting each dielectric sidewall structureto form a self-aligned double patterned permanent dielectric structure.2. The method of claim 1 wherein said forming the patterned photoresistincludes selecting a positive-tone photoresist or a negative-tonephotoresist, depositing the positive-tone photoresist or negative-tonephotoresist, pattern-wise exposing the positive-tone photoresist ornegative-tone photoresist, and developing the pattern-wised exposedpositive-tone photoresist or negative-tone photoresist.
 3. The method ofclaim 1 wherein said forming the dielectric sidewall structure includesoverfilling the at least one opening with a dielectric coating material,baking to cause diffusion of residual acid from sidewalls of thepatterned photoresist into neighboring sidewall portions of thedielectric coating material and crosslinking of said neighboringsidewall portions of the dielectric coating material, and removingnon-crosslinked portions of the dielectric coating material relative tothe crosslinked neighboring sidewall portions of the dielectric coatingmaterial.
 4. The method of claim 3 wherein said dielectric coatingmaterial comprises a functionalized polymer, copolymer, or a blendincluding at least two of any combination of polymers and/or copolymershaving one or more acid-sensitive reactive groups.
 5. The method ofclaim 1 wherein said patterned photoresist includes a patternedpermanent anti-reflective coating directly below the patternedphotoresist.
 6. The method of claim 1 further comprising forming aprotective layer on said patterned photoresist.
 7. The method of claim 1wherein said converting each dielectric sidewall structure into theself-aligned double patterned permanent dielectric structure comprises athermal cure, an electron beam cure, an ultra-violet (UV) cure, an ionbeam cure, a plasma cure, a microwave cure or a combination thereof. 8.The method of claim 1 further comprising forming at least anelectrically conductive material within the narrowed width opening andthe additional openings after said converting of each dielectricsidewall structure into the self-aligned double patterned permanentdielectric structure.
 9. The method of claim 8 further comprisingetching portions of the substrate that are exposed by said narrowedwidth opening and the additional openings prior to forming theelectrically conductive material.
 10. A method of forming a self-alignedpermanent on-chip dual-damascene interconnect structure comprisingproviding a patterned dielectric material having a plurality of firstopenings on an upper surface of a substrate; forming a patternedphotoresist having second openings atop the patterned dielectricmaterial, wherein a portion of said patterned photoresist remains in atleast one of said plurality of first openings; forming a dielectricsidewall structure on each sidewall of the patterned photoresist withinsaid second openings and atop an upper surface of the patterneddielectric material, wherein said dielectric sidewall structure narrowsthe second openings providing narrowed width second openings; removingthe patterned photoresist to provide a third opening between neighboringdielectric sidewall structures, wherein said narrowed width secondopenings and said third opening are located atop and are connected withone of said plurality of first openings; converting each dielectricsidewall structure into a self-aligned permanent patterned dielectricstructure; and filling each opening with at least an electricallyconductive material
 11. The method of claim 10 wherein said forming thepatterned photoresist includes selecting a positive-tone photoresist ora negative-tone photoresist, depositing the positive-tone photoresist ornegative-tone photoresist, pattern-wise exposing the positive-tonephotoresist or negative-tone photoresist, and developing thepattern-wised exposed positive-tone photoresist or negative-tonephotoresist.
 12. The method of claim 11 wherein said forming thedielectric sidewall structure providing a dielectric coating material,baking to cause diffusion of residual acid from sidewalls of thepatterned photoresist into neighboring sidewall portions of thedielectric coating material and cros slinking of said neighboringsidewall portions of the dielectric coating material, and removingnon-crosslinked portions of the dielectric coating material relative tothe crosslinked neighboring sidewall portions of the dielectric coatingmaterial.
 13. The method of claim 12 wherein said dielectric coatingmaterial comprises a functionalized polymer, copolymer, or a blendincluding at least two of any combination of polymers and/or copolymershaving one or more acid-sensitive reactive groups.
 14. The method ofclaim 10 wherein said patterned dielectric material includes a patternedanti-reflective coating directly below the patterned dielectricmaterial.
 15. The method of claim 10 wherein said converting eachdielectric sidewall structure into the self-aligned permanent patterneddielectric structure comprises a thermal cure, an electron beam cure, anultra-violet (UV) cure, an ion beam cure, a plasma cure, a microwavecure or a combination thereof.
 16. The method of claim 10 wherein saidsubstrate includes an antireflective coating and an optional dielectriccap, and wherein exposed positions of said antireflective coating and,if present, the optional dielectric cap are etched prior to filling thefirst, the second and the third openings with at least an electricallyconductive material
 17. A dielectric composition comprising: afunctionalized polymer, copolymer, or a blend including at least two ofany combination of polymers and/or copolymers having one or moreacid-sensitive reactive groups; and at least one solvent that iscompatible with photoresist patterns.
 18. The composition of claim 17wherein said solvent is a hydrocarbon, an alcohol or water.
 19. Aninterconnect structure comprising: at least one patterned dielectriclayer located on a substrate, wherein said at least one patterneddielectric layer includes differently sized conductive features embeddedtherein, said differently sized conductive features are laterallyadjacent to each other and are located at a same interconnect level. 20.The interconnect structure of claim 19 wherein alternating laterallyadjacent conductive features of said interconnect structure are of asame size.
 21. The interconnect structure of claim 19 further comprisinga patterned antireflective coating located beneath the at least onepatterned dielectric layer.
 22. The interconnect structure of claim 21further comprising a patterned dielectric cap layer located beneath thepatterned antireflective coating.
 23. The interconnect structure ofclaim 19 wherein said interconnect structure is a single damasceneinterconnect structure.
 24. The interconnect structure of claim 19wherein said interconnect structure is a dual damascene interconnectstructure.
 25. The interconnect structure of claim 19 wherein said atleast one patterned dielectric layer is comprised of a cured reactionproduct of an acid catalyzed crosslinked functionalized polymer,copolymer, or a blend including at least two of any combination ofpolymers and/or copolymers having one or more acid-sensitive reactivegroups.